Haemophilus influenzae infection: Difference between revisions

	Haemophilus influenzae infection Main page
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Overview
Causes
Classification Pneumonia Bacteremia Meningitis Epiglottitis Cellulitis arthritis Otitis media Conjunctivitis
Pathophysiology

Haemophilus influenzae
	; H. influenzae on a blood agar plate.
Scientific classification
Kingdom:	Bacteria;
Phylum:	Proteobacteria;
Class:	Gamma Proteobacteria;
Order:	Pasteurellales;
Family:	Pasteurellaceae;
Genus:	Haemophilus;
Species:	H. influenzae;
Binomial name
	Haemophilus influenzae; (Lehmann & Neumann 1896); Winslow et al. 1917

VisualWikitext

Latest revision as of 21:56, 29 July 2020

This page is about clinical aspects of the disease. For microbiologic aspects of the causative organism(s), see Haemophilus influenzae.

For patient information about Haemophilus influenzae infection, click here | Haemophilus influenzae type b (Hib) vaccine, click here.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Synonyms and keywords: Hib disease

Overview

H.influenzae is a gram-negative, cocco-bacillary, facultatively anaerobic pathogenic bacterium that can cause infections in people of all ages ranging from mild, such as an ear infection, to severe, such as a bloodstream infection. It is a normal commensal of nose and throat and does not cause any infection under normal situations. But when the host defense mechanisms are weakened it invades the epithelium and disseminates to other parts of the body where it causes infection.^[1]

Causes

Haemophilus influenza infections are caused by the bacterium Haemophilus influenza.
It is a is a gram-negative, cocco-bacillary, facultatively anaerobic bacterium.
Based on their distinct capsular antigens they are grouped into capsular (typeable) and non-capsulate (nontypeable)
There are six identifiable types of H.influenza (a, b, c, d, e, and f)
H. influenza type b is the most common type among capsular H.influeza.
These bacteria are a normal commensal of throat and nose. However, the bacteria can sometimes move to other parts of the body and cause infection.

Classification

H. influenzae, including Hib, can cause many different kinds of infections. These infections can range from mild ear infections to severe diseases, like bloodstream infections. When the bacteria invade parts of the body, like spinal fluid or blood, this is known as "invasive disease." Invasive disease is usually severe and can sometimes result in death.
The most common types of invasive disease caused by H.influenza are:

The most common types of non-invasive disease caused by H.influenza are:

H influenza infection

Infection due to capsulated H influenzae(Invasive)

Infection due to non-capsulated H influenzae(Non-invasive)

Pathophysiology

The pathogenesis of H.influenzae infections can be described as follows:^[2]^[3]

Transmission

Transmission is by direct contact or by inhalation of respiratory tract droplets.
Neonates can acquire the infection by aspiration of amniotic fluid or contact with genital tract secretions containing the bacteria.

Incubation period

The incubation period (time between exposure and first symptoms) of H. influenzae disease is not certain but could be as short as 7 days.

Seeding

A larger bacterial load or the presence of a concomitant viral infection can potentiate the infection.
The colonizing bacteria invade the mucosa and enter the bloodstream.
The spread of bacteria by direct extension to the eustachian tubes causes otitis media.
Spread to the sinuses leads to sinusitis.
Spread down the respiratory tract results in bronchitis and pneumonia.
Eustachian tube dysfunction, antecedent viral upper respiratory tract infection (URTI), foreign bodies, and mucosal irritants, including smoking, can promote infection.
In patients with underlying chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF), non-typeable H influenza frequently colonizes the lower respiratory tract and can exacerbate the disease.

Pathogenesis

The capsule of H influenza plays a key role in the pathogenesis of the all the capsulated H influenza infections.
The antiphagocytic nature of the Hib capsule makes it resistant to natural host phagocytic defense mechanisms and facilitating bacterial proliferation.
After proliferation, the bacterial load disseminates to various sites, including meninges, subcutaneous tissue, joints, pleura, pericardium, and lungs triggering an inflammatory response and subsequently activating the complement system.
Capsulated H influenza can penetrate the normal epithelium and are therefore responsible for invasive infections.
Non-capsulated are non-invasive but can still induce the inflammatory response similar to that of capsulated organisms
The Hib conjugate vaccine induces protection by inducing antibodies against the PRP capsule.
The Hib conjugate vaccine does not provide protection against Non-typable H influenza strains. Since the widespread use of the Hib conjugate vaccine, Non-typable H influenza strains has become more of a pathogen.

References

↑ "Pinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC".
↑ Duell BL, Su YC, Riesbeck K (2016). "Host-pathogen interactions of nontypeable Haemophilus influenzae: from commensal to pathogen". FEBS Lett. 590 (21): 3840–3853. doi:10.1002/1873-3468.12351. PMID 27508518.
↑ Close RM, Pearson C, Cohn J (2016). "Vaccine-preventable disease and the under-utilization of immunizations in complex humanitarian emergencies". Vaccine. 34 (39): 4649–55. doi:10.1016/j.vaccine.2016.08.025. PMID 27527818.

Template:WikiDoc Sources

[urlPinkbook_|_Hib_|_Epidemiology_of_Vaccine_Preventable_Diseases_|_CDC-1] "Pinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC".

[pmid27508518-2] Duell BL, Su YC, Riesbeck K (2016). "Host-pathogen interactions of nontypeable Haemophilus influenzae: from commensal to pathogen". FEBS Lett. 590 (21): 3840–3853. doi:10.1002/1873-3468.12351. PMID 27508518.

[pmid27527818-3] Close RM, Pearson C, Cohn J (2016). "Vaccine-preventable disease and the under-utilization of immunizations in complex humanitarian emergencies". Vaccine. 34 (39): 4649–55. doi:10.1016/j.vaccine.2016.08.025. PMID 27527818.

[1]

[2]

[3]

@@ Line 1: / Line 1: @@
-[[Image:Haemophilus i..jpg|thumb|220px|Haemophilus influenzae on a blood agar plate]]
+__NOTOC__
-{{SI}}
+{{Taxobox
-{{CMG}}
+| color = lightgrey
+| name = ''Haemophilus influenzae''
+| image = Haemophilus influenzae 01.jpg
+| image_width = 200px
+| image_caption = ''H. influenzae'' on a [[Blood agar#Blood agar types|blood agar]] plate.
+| regnum = [[Bacterium|Bacteria]]
+| phylum = [[Proteobacteria]]
+| classis = [[Gamma Proteobacteria]]
+| ordo = [[Pasteurellaceae|Pasteurellales]]
+| familia = [[Pasteurellaceae]]
+| genus = ''[[Haemophilus]]''
+| species = '''''H. influenzae'''''
+| binomial = ''Haemophilus influenzae''
+| binomial_authority = (Lehmann & Neumann 1896)<br>Winslow ''et al.'' 1917
+}}
+{{Haemophilus influenzae infection}}
+{{About1|Haemophilus influenzae}}
+'''For patient information about Haemophilus influenzae infection, click [[Haemophilus influenzae infection (patient information)|here]] | Haemophilus influenzae type b (Hib) vaccine, click [[Haemophilus influenzae Type b (Hib) Vaccine (patient information)|here]].'''<br><br>
+{{CMG}} ; {{AE}} {{ADG}} <br>
 {{SK}} Hib disease
+==Overview==
+[[Haemophilus influenzae|H.influenzae]]  is a [[gram-negative]], [[Coccobacillus|cocco-bacillary]], [[Facultative anaerobic organism|facultatively anaerobic]] pathogenic bacterium that can cause infections in people of all ages ranging from mild, such as an ear infection, to severe, such as a bloodstream infection. It is a normal [[commensal]] of [[nose]] and [[throat]] and does not cause any infection under normal situations. But when the host [[Defence mechanism|defense mechanisms]] are weakened it invades the [[epithelium]] and [[Disseminated disease|disseminate]]<nowiki/>s to other parts of the body where it causes [[infection]].<ref name="urlPinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC">{{cite web |url=https://www.cdc.gov/vaccines/pubs/pinkbook/hib.html |title=Pinkbook &#124; Hib &#124; Epidemiology of Vaccine Preventable Diseases &#124; CDC |format= |work= |accessdate=}}</ref>
-== Overview ==
+==Causes==
+*[[Haemophilus influenzae|Haemophilus influenza]] infections are caused by the bacterium [[Haemophilus influenza]].
-Infection with the bacterium Haemophilus influenzae type b (Hib) can result in meningitis and other severe infections (e.g., pneumonia, bacteremia, cellulitis, septic arthritis, and epiglottitis) primarily among infants and children <5 years of age.
+*It is a is a [[gram-negative]], [[Coccobacillus|cocco-bacillary]], [[Facultative anaerobic organism|facultatively anaerobic]] bacterium.
+*Based on their distinct capsular antigens they are grouped into capsular (typeable) and non-capsulate  (nontypeable)
-== Epidemiology and Demographics ==
+*There are six identifiable types of [[Haemophilus influenzae|H.influenza]] (a, b, c, d, e, and f)
+*[[H. influenza infection|H. influenza type b]] is the most common type among capsular H.influeza.
-During 1980-1990, incidence was 40-100/100,000 children < 5 years old in the United States. Due to routine use of the Hib conjugate vaccine since 1990, the incidence of invasive Hib disease has decreased to 1.3/100,000 children. However, Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where vaccine is not widely used.
+*These bacteria are a normal [[commensal]] of throat and nose. However, the [[bacteria]] can sometimes move to other parts of the body and cause infection.
-Invasive Hib disease is endemic throughout the world. In countries that have achieved high coverage with routine Hib vaccination programs, Hib disease has become rare. In 2004, most countries in Western Europe, South America, and Central America had initiated routine Hib vaccination (http://www.who.int/mediacentre/factsheets/fs294/en/). However, Hib disease remains common in many developing countries and is estimated to cause 2-3 million cases of serious disease in young children annually.
-Hib disease is uncommon in anyone 5 years of age or older. Hib meningitis has a case-fatality ratio of 5-10% in the United States even with initiation of early antimicrobial therapy. As a result of the widespread use of conjugate Hib vaccines, the disease is now uncommon in the United States and is seen primarily in infants too young to be vaccinated and unvaccinated children. In 2004, the estimated annual incidence of Hib was 0.15 cases per 100,000 in children younger than 5 years of age.
-'''Trends'''
-Since licensure of conjugate vaccines for infants (1990) and children (1987), rates of disease among children <5 years old have declined by more than 95% in the United States, while rates for adults have remained stable. However, rates of disease among Alaskan natives remain higher than elsewhere in the United States.
-== Risk Factors ==
-Infants and young children, household contacts, and day-care classmates are at higher tisk of aquiring Haemophilus influenzae serotype B infection.
-'''Risk for travelers'''
-Unvaccinated infants and children aged less than 5 years who travel may be at risk for serious Hib disease, especially if traveling to a country that does not use Hib vaccine. In addition, adults who have been splenectomized have an increased risk of infections.
-== Pathophysiology & Etiology==
-'''Etiologic agent'''
-Haemophilus influenzae serotype b.
-'''Transmission'''
-Direct contact with respiratory droplets from nasopharyngeal carrier or case patient.
-== Natural History ==
-Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, is a non-motile Gram-negative coccobacillus first described in 1892 by Richard Pfeiffer during an influenza pandemic. It is generally aerobic, but can grow as a facultative anaerobe. H. influenzae was mistakenly considered to be the cause of the common flu until 1933, when the viral etiology of the flu became apparent. Still, H. influenzae is responsible for a wide range of clinical diseases.
-Because of its small genome, H. influenzae became the first free-living organism with its entire genome sequenced. Its genome consists of 1,830,140 base pairs of DNA and contains 1740 genes. The method used was Whole genome shotgun. The sequencing project, completed and published in Science in 1995, was conducted at The Institute for Genomic Research.
+==Classification==
+[[Haemophilus influenzae|H. influenzae]], including Hib, can cause many different kinds of [[infections]]. These infections can range from mild ear infections to severe diseases, like bloodstream infections. When the bacteria invade parts of the body, like [[spinal fluid]] or [[blood]], this is known as "invasive disease." Invasive disease is usually severe and can sometimes result in death.<br>
+The most common types of invasive disease caused by H.influenza are:
+*[[Pneumonia]]
+*[[Bacteremia]]
+*[[Meningitis]]
+*[[Epiglottitis]]
+*[[Cellulitis]]
+*Infectious [[arthritis]]
+The most common types of non-invasive disease caused by H.influenza are:
+*[[Otitis media]]
+*[[Conjunctivitis]]
+<small>
+{{Family tree/start}}
+{{Family tree | | | | | | | | | | | | | | | | | | | | | | | A01 | | | | | | | | | | | | |A01= '''[[H influenza infection]]'''}}
+{{Family tree | | | | | | | | | | |,|-|-|-|-|-|-|-|-|-|-|-|-|^|-|-|-|-|-|-|-|-|-|-|-|-|-|.| | }}
+{{Family tree | | | | | | | | | | C01 | | | | | | | | | | | | | | | | | | | | | | | | | C02 |C01= Infection due to capsulated [[Haemophilus influenzae|H influenzae]](Invasive)| C02= Infection due to non-capsulated [[Haemophilus influenzae|H influenzae]](Non-invasive)}}
+{{Family tree | | |,|-|-|-|v|-|-|-|^|-|-|-|v|-|-|-|v|-|-|-|v|-|-|-|.| | | | | |,|-|-|-|-|^|-|-|-|-|.|}}
+{{Family tree | | D01 | | D02 | | | | | | D03 | | D04 | | D05 | | D06 | | | | D07 | | | | | | | | D08 |D01= [[Meningitis]] |D02=[[Cellulitis]]|D03=[[Epiglottitis]] |D04= [[Pneumonia]]|D05=[[Pericarditis]]|D06=[[Septic arthritis]]|D07=[[otitis media]]|D08=[[Conjunctivitis]]}}
+{{Family tree/end}}</small>
-== Diagnosis ==
+==Pathophysiology==
+The pathogenesis of H.influenzae infections can be described as follows:<ref name="pmid27508518">{{cite journal |vauthors=Duell BL, Su YC, Riesbeck K |title=Host-pathogen interactions of nontypeable Haemophilus influenzae: from commensal to pathogen |journal=FEBS Lett. |volume=590 |issue=21 |pages=3840–3853 |year=2016 |pmid=27508518 |doi=10.1002/1873-3468.12351 |url=}}</ref><ref name="pmid27527818">{{cite journal |vauthors=Close RM, Pearson C, Cohn J |title=Vaccine-preventable disease and the under-utilization of immunizations in complex humanitarian emergencies |journal=Vaccine |volume=34 |issue=39 |pages=4649–55 |year=2016 |pmid=27527818 |doi=10.1016/j.vaccine.2016.08.025 |url=}}</ref>
-=== History and Symptoms ===
+===Transmission===
+*Transmission is by direct contact or by inhalation of respiratory tract droplets.
-Before the availability of the Haemophilus influenzae serotype b (Hib) conjugate vaccine in the United States and other industrialized countries, more than one-half of Hib cases presented as [[meningitis]] with [[fever]], [[headache]], and stiff neck. The remainder presented as [[cellulitis]], [[arthritis]], or [[sepsis]]. In developing countries, Hib is still a leading cause of bacterial pneumonia deaths in children.
+*[[Neonates]] can acquire the infection by [[aspiration]] of [[amniotic fluid]] or contact with genital tract secretions containing the bacteria.
+===Incubation period===
-== Risk Stratification and Prognosis==
+The [[incubation period]] (time between exposure and first symptoms) of [[Haemophilus influenzae|H. influenzae]] disease is not certain but could be as short as 7 days.
+===Seeding===
-%-6% of cases are fatal; up to 20% of surviving patients have permanent hearing loss or other long-term sequelae.
+*A larger bacterial load or the presence of a concomitant viral infection can potentiate the infection.
+*The colonizing bacteria invade the mucosa and [[Bacteremia|enter the bloodstream]].
-== Treatment ==
+*The spread of bacteria by direct extension to the eustachian tubes causes [[otitis media]].
+*Spread to the sinuses leads to [[Sinusitis|sinusitis.]]
-Specific parenteral antibiotic treatment is necessary for invasive Hib disease, and immediate airway stabilization is necessary for epiglottitis. Antibiotic prophylaxis with rifampin is indicated for all household contacts in the following circumstances: households with a contact aged 4 years or younger who is unimmunized or underimmunized, households with a child aged younger than 12 months who has not received the primary series, and households with an immunocompromised child. Chemoprophylaxis is not recommended for pregnant women or for child care contacts with a single index case, but the children’s vaccination history should be reviewed to ensure completion of the recommended schedule of Hib conjugate vaccine. A 4-day course of rifampin eradicates Hib carriage from the pharynx in approximately 95% of carriers.
+*Spread down the respiratory tract results in [[bronchitis]] and [[pneumonia]].
+*[[Eustachian tube dysfunction]], antecedent viral upper respiratory tract infection ([[Upper respiratory tract infection|URT]]I), foreign bodies, and mucosal irritants, including smoking, can promote infection.
-=== Primary Prevention ===
+*In patients with underlying [[chronic obstructive pulmonary disease]] ([[Chronic obstructive pulmonary disease|COPD]]) or [[cystic fibrosis]] ([[Cystic fibrosis|CF]]), non-typeable [[Haemophilus influenzae|H influenza]] frequently colonizes the [[Lower respiratory tract|lower respiratory trac]]<nowiki/>t and can exacerbate the disease.
+===Pathogenesis===
-[[Haemophilus Influenzae Type b (Hib) Vaccine]]
+*The [[capsule]] of [[Hemophilus influenza infection|H influenza]] plays a key role in the pathogenesis of the all the capsulated H influenza infections.
+*The [[antiphagocytic]] nature of the Hib capsule makes it resistant to natural host phagocytic defense mechanisms and facilitating bacterial proliferation.
-=== Future or Investigational Therapies ===
+*After proliferation, the bacterial load disseminates to various sites, including [[meninges]], [[subcutaneous tissue]], [[joints]], [[Pleurae|pleura]], [[pericardium]], and [[lungs]] triggering an inflammatory response and subsequently activating the [[complement system]].
+*Capsulated H influenza can penetrate the normal epithelium and are therefore responsible for invasive infections.
-'''Challenges'''
+*Non-capsulated are non-invasive but can still induce the inflammatory response similar to that of capsulated organisms
+*The Hib [[conjugate vaccine]] induces protection by inducing antibodies against the PRP capsule.
-Elimination of persistent Hib disease in the United States. Currently available conjugate vaccines differ in immuno-genicity in very young children and possibly in duration of antibody persistence, raising questions about long-term efficacy (>5 years), optimal use, and schedules. Monitoring the possible emergence of disease due to other serotypes. Problems with serotyping of H. influenzae in state health departments. Development of rapid molecular assays for detection and molecular subtyping of all Hi strains. The cost of Hib conjugate vaccines has limited their use in developing countries even though Hib is a major cause of morbidity and mortality.
+*The Hib conjugate vaccine does not provide protection against Non-typable H influenza strains. Since the widespread use of the Hib conjugate vaccine,  Non-typable H influenza strains has become more of a pathogen.
-'''Opportunities'''
-Evaluating the characteristics of Hib vaccines associated with prevention of carriage and invasive disease will facilitate application of this technology to development of conjugate vaccines for other organisms with polysaccharide capsules (such as the meningococcus, pneumococcus, and group B streptococcus). Further evaluation of herd immunity effects may lead to insight into vaccination strategies that optimize protection against invasive disease and transmission of Hib organisms.
 ==References==
+{{reflist|2}}
-#http://www.cdc.gov/ncidod/dbmd/diseaseinfo/histoplasmosis_g.htm
-#http://en.wikipedia.org/wiki/Haemophilus_influenzae
-#http://wwwn.cdc.gov/travel/yellowBookCh4-FluMeningitis.aspx
-== Acknowledgements ==
-The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.
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